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Home Insert Draw Design Layout References Mailings » Calibri (Body) -|11 A ^ A As, AP Paste Mutations What exactly does the word "mutation" mean? What are the three types of mutation found in genes (or other single sequences)? One of the above mutations is also called a "point" mutation. Which one is a point mutation and why? What is the difference between a "transition" and a "transversion"? Why do you think transversions would be more rare? There are various ways that a mutation can alter the coding sequence in a gene. What is the meaning of each of the following: Silent mutation, missense mutation, nonsense mutation? What happens if an insertion or deletion mutation does not consist of a multiple of three nucleotides? what is this called What is "polarity" in relation to these gene mutations? Mutations outside the coding sequence can speed up or slow down transcription. What are these mutations called and which is which? What is a "position effect"? The wild type genotype gives us a baseline to determine which alleles are mutant alleles. What is a wild type genotype? What is a reversion? What is a conditional mutant? What is a "position effect"? What are some of the causes of position effects? What is the difference between germ-line and somatic cell mutations? Which one is heritable? Somatic cell mutations and mutations on the X can result in a genetic mosaic. What is that and why would anX mutation cause a mosaic and in which sex? Be sure to review the two experiments that showed that mutations are random events. Be able to associate the names with each experiment. One is in the reading and one is in the lecture. What is the difference between spontaneous and induced mutations? Give a short list of possible causes of each. See Table 19.4. Know the descriptions of possible causes, not just the category names What are depurination, deamination and tautomeric shifts? What nucleotides/bases are involved and how do they change? Why do methylated cytosines produce hotspots for mutation? What is a trinucleotide repeat and why is it a hotspot for mutation? What is a TNRE? What are some of the human diseases caused bv TNREs? Which codon (and which amino acid) are usually involved in

Explanation / Answer

Answer-

1.Exact meaning of word mutation- Word Mutation means a change or an alteration as in nature of form.

by definition in biology mutation is the permanent change in the nucleotide base sequence of the genome of an organism.

2.Three types of mutation found in genes-

1. Point mutations- These are small significant changes which are often occur in a single nucleotide base.

2. Deletions- It is removal of information from the gene and it could be as small as a single base or as large as the gene itself.

3.Insertions- It occurs when extra DNA is added into an existing gene.

One More is Frameshift mutation in which there can be deletion of insertion of one or two nucleotide base, when this occurs the reading frame is changed so that all the codons read after the mutation are incorrect, even though the bases themselves may be still present there in the gene.

3.Point mutaion - These are small significant changes which are often occur in a single nucleotide base.

Sickle cell anemia in human is a point mutation, normally, glutamic acid is produced in the chain, but the substitution causes valine to be produced at that spot instead, the mutation cause a single nucleotide substitution from A to T in the codon for amino acid 6, the change converts a glutamic acid codon GAG to a valine codon GTG this form of hemoglobin in persons with sickle cell anemia is referred to as HbS.

4.Difference between transition and transversion

Transition- When a purine changes to a different purine or a pyrimidine changes to a different pyrimidine e.g. adenine to guanine or cytisine to thymine .

Transversion- When a purine changes to a pyrimidine or a pyramidine changes into a purine e.g. adenine to cytosine or guanine to thymine.

Transversion is rare because the generation of transversions requires much greater distortion of the double helix because in transversion when base substituted there is change in no. of carbon in nitrogenous base and also addition of an extra ring structure as change from pyrimidine to purine or breaking of a ring structure when changes from purine to pyrimidine, and the base pair formed during the production of transversion mutations is either much larger which involving two purines or much smaller which involve two pyrimidines than the standard base pair. So in citation of these reasons transversion is rare than transition.

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